Bond fixture for leading edge assembly

ABSTRACT

A bond fixture includes a frame defining a chamber for receiving a component. At least one bladder assembly is connected to the frame. The at least one bladder assembly includes a pad for contacting the component. A position of the pad relative to the component is controlled by a pressure of the bladder assembly. A caul assembly is adapted to thermally couple to the component to heat a localized portion of the component.

BACKGROUND OF THE INVENTION

Exemplary embodiments of the invention relate to a rotary-wing aircraftand, more particularly, to a bond fixture for use during the manufactureor repair of a rotor blade of a rotary-wing aircraft.

Rotary wing aircraft include a plurality of main rotor blades coupled toa central hub. The rotor blades include aerodynamic surfaces that, whenrotated, create lift. The configuration of the main rotor blades,particularly the leading edge thereof, is selected to enhance rotorblade performance, for example to increase the hover and liftcapabilities of the rotary-wing aircraft. Rotor blades are subjected tohigh stresses and strains resulting from aerodynamic forces developedduring operation.

BRIEF DESCRIPTION OF THE INVENTION

According to one embodiment of the invention, a bond fixture includes aframe defining a chamber for receiving a component. At least one bladderassembly is connected to the frame. The at least one bladder assemblyincludes a pad for contacting the component. A position of the padrelative to the component is controlled by a pressure of the bladderassembly. A caul assembly is adapted to thermally couple to thecomponent to heat a localized portion of the component.

In addition to one or more of the features described above, or as analternative, in further embodiments the pad of the at least one bladderassembly has a contour complementary to the component.

In addition to one or more of the features described above, or as analternative, in further embodiments the at least one bladder assemblyincludes a first bladder assembly mounted to a first portion of theframe and a second bladder assembly mounted to a second portion of theframe.

In addition to one or more of the features described above, or as analternative, in further embodiments the first bladder assembly and thesecond bladder assembly are arranged in fluid communication with apressure source.

In addition to one or more of the features described above, or as analternative, in further embodiments a pressure is equalized between thefirst bladder assembly and the second bladder assembly.

In addition to one or more of the features described above, or as analternative, in further embodiments the caul assembly includes a heater.

In addition to one or more of the features described above, or as analternative, in further embodiments the caul assembly further includesan inner caul and an outer caul and the heater is positioned between theinner caul and the outer caul.

In addition to one or more of the features described above, or as analternative, in further embodiments heat output by the heater is uniformacross the rotor blade.

In addition to one or more of the features described above, or as analternative, in further embodiments heat output by the heater variesacross the rotor blade.

In addition to one or more of the features described above, or as analternative, in further embodiments comprising at least one strapassociated with the frame to secure the bond fixture to the component.

In addition to one or more of the features described above, or as analternative, in further embodiments comprising a trailing edge guardmounted to the component opposite the frame.

In addition to one or more of the features described above, or as analternative, in further embodiments the bond fixture and the trailingedge guard cooperate to affix to the component.

In addition to one or more of the features described above, or as analternative, in further embodiments comprising a cuff guard mounted to aportion of the component, opposite the frame.

According to another embodiment, a method of bonding a leading edgefairing to a rotor blade includes installing the leading edge fairingabout the rotor blade and mounting a bond fixture about the leading edgefairing. Localized and constant heat and pressure is applied to theleading edge fairing via the bond fixture.

In addition to one or more of the features described above, or as analternative, in further embodiments comprising installing a caulassembly about the leading edge fairing, the caul assembly beingpositioned within the bond fixture.

In addition to one or more of the features described above, or as analternative, in further embodiments mounting the bond fixture to therotor blade includes tightening at least one strap about the bondfixture and the rotor blade.

In addition to one or more of the features described above, or as analternative, in further embodiments mounting the bond fixture to therotor blade includes coupling the bond fixture to at least one of atrailing edge guard and a cuff guard mounted to the rotor blade,opposite the bond fixture.

In addition to one or more of the features described above, or as analternative, in further embodiments comprising connecting a power sourceto the bond fixture to apply heat to the leading edge fairing.

In addition to one or more of the features described above, or as analternative, in further embodiments comprising connecting an air supplyto the bond fixture to apply pressure to the leading edge fairing.

In addition to one or more of the features described above, or as analternative, in further embodiments pressure applied to the rotor bladeby a pad is adjusted when air form an air supply is provided to abladder operably coupled to the pad.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of an example of a rotary wing aircraft;

FIG. 2 is a perspective view of an example of a rotor blade of a rotarywing aircraft;

FIG. 3 is a perspective view of a rotor blade having a bond assemblymounted thereto according to an embodiment;

FIG. 4 is a perspective view of a bond assembly according to anembodiment;

FIG. 5 is a front view of the bond assembly according to an embodiment;

FIG. 6 is a detailed perspective view of a first bond fixture of thebond assembly according to an embodiment; and

FIG. 7 is a cross-sectional view of the first bond fixture according toan embodiment;

FIG. 8 is a perspective view of a caul assembly according to anembodiment; and

FIG. 9 is a method of using the bond fixture to adhere a leading edgefairing according to an embodiment.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 schematically illustrates a rotary-wing aircraft 10 having a mainrotor system 12. The aircraft 10 includes an airframe 14 having anextending tail 16 which mounts a tail rotor system 18, such as ananti-torque system for example. The main rotor assembly 12 is drivenabout an axis of rotation A through a main gearbox (illustratedschematically at T) by one or more engines E. The main rotor system 12includes a plurality of rotor blade assemblies 20 mounted to a rotor hubassembly H. Although a particular helicopter configuration isillustrated and described in the disclosed non-limiting embodiment,other configurations and/or machines, such as high speed compoundrotary-wing aircraft with supplemental translational thrust systems,dual contra-rotating, coaxial rotor system aircraft, turbo-props,tilt-rotors, and tilt-wing aircraft are also within the scope of theinvention.

Referring to FIG. 2, each rotor blade assembly 20 of the rotor assembly12 generally includes a root section 22, an intermediate section 24, atip section 26, and a tip cap 28. Each rotor blade section 22, 24, 26,28 may define particular airfoil geometries to tailor the rotor bladeaerodynamics to the velocity increase along the rotor blade span. As,illustrated, the rotor blade tip section 26 may include an anhedral form27 (not shown); however, a tip section having any angled or non-angledform such as cathedral, gull, bent, and other non-straight forms arealso contemplated herein.

The rotor blade sections 22-28 define a span R of the main rotor bladeassembly 20 between the axis of rotation A and a distal end 30 of thetip cap 28 such that any radial station may be expressed as a percentagein terms of a blade radius x/R. The rotor blade assembly 20 defines alongitudinal feathering axis P between a leading edge 32 and a trailingedge 34. The distance between the leading edge 32 and the trailing edge34 defines a main element chord length Cm. In an embodiment, a leadingedge fairing 36 is mounted to the leading edge 32 of the rotor blade 20at the root section 22 of the rotor blade 20, adjacent the blade cuff38. The leading edge fairing 36 at least partially defines an airfoilcontour of the rotor blade 20.

A bond assembly 40 for bonding the leading edge fairing 36 to the rotorblade 20 is illustrated in FIGS. 3-8. The bond assembly 40 includes afirst fixture 50 configured to mount about the leading edge 32 of therotor blade 20. The first fixture 50 includes one or more generally U orC-shaped frames 52 having a first arm 54 and second arm 56 coupled at afirst end thereof. The first and second arm 54, 56, may but need not besubstantially identical. In the illustrated, non-limiting embodiment,the first and second arms 54, 56 are arranged parallel to and oppositeone another in a generally aligned manner such that the first and secondarms 54, 56 are separated by a distance. In an embodiment, a handle 58is mounted to a portion of the frame 52, such as an exterior surfacethereof for example, to aid in installation and removal of the firstfixture 50.

The frame 52 defines a chamber 60 within which the leading edge 32 ofthe rotor blade 20 is positionable. In the illustrated, non-limitingembodiment, a pad 64 is mounted to the portion 62 of the frame 52coupling the first and second arms 54, 56 within the chamber 60. The pad64 has an inlet 66 (FIG. 7) formed therein having a contour generallycomplementary to the leading edge 32 of the rotor blade 20. As a result,when the bond assembly 40 is mounted to a rotor blade 20, the leadingedge 32 is disposed within the inlet 66. In other embodiments, the inlet66 may be integrally formed with the frame 52. It should be understoodthat the frame 52 illustrated and described herein is intended as anexample only and that a frame 52 having another configuration is alsowithin the scope of the disclosure.

In the illustrated, non-limiting embodiment, the first fixture 50includes a plurality of frames 52 mounted at different positions overthe span of the rotor blade 20 within the root section 22. However,other configurations, such as where a frame 52 extends over the span ofthe rotor blade 20 a distance substantially equal to the leading edgefairing 36 for example, are contemplated herein.

Connected to or integrally formed with a first surface 68 of the firstarm 54, adjacent the chamber 60, is a first bladder assembly 70. Inembodiments where the first fixture 50 includes a plurality of frames52, the fixture 50 may include a plurality of first bladders assemblies70, or alternatively may include a single first bladder assembly 70coupled to the first arm 54 of each of the plurality of frames 52.Similarly, a second bladder assembly 72 is connected to or integrallyformed with a first surface 74 of the second arm 56, adjacent thechamber 60. In embodiments where the first fixture 50 includes aplurality of frames 52, the fixture 50 may include a plurality of secondbladders assemblies 72, or alternatively may include a single secondbladder assembly 72 coupled to the second arm 56 of each of theplurality of frames 52.

In an embodiment, each first bladder assembly and second bladderassembly comprises a bladder 76 coupled to a pad 78. The pad 78 may beformed from any suitable material that does not damage the surface rotorblade 20 when applying pressure thereto. The pad 78 of the first bladderassembly 70 is configured to apply pressure to a first, upper surface ofthe rotor blade 20 and the pad 78 of the second bladder assembly 72 isconfigured to apply pressure to a second, lower surface of the rotorblade 20. As a result, the pad 78 of each assembly 70, 72 is formed witha contour generally complementary to the rotor blade 20.

As air pressure is provided to a bladder 76, the bladder is configuredto move the corresponding pad 78 into contact with the rotor blade 20.One or more passages, such as formed by conduits 80, fluidly couple thefirst bladder assembly 70 and the second bladder assembly 72 with an airsource (not shown). As a result, the pressure generated by the airsource may be equalized between the first and second bladder assemblies70, 72. However, embodiments where the pressure between the first andsecond bladder assemblies 70, 72 is uneven or embodiments where thebladder assemblies 70, 72 are independently operable are alsocontemplated herein.

In an embodiment, a caul assembly 82 (FIG. 8) may be positioned aboutthe leading edge 32 of the rotor blade 20, in overlapping arrangementwith the leading edge fairing 36, before the first fixture 50 is mountedto the rotor blade 20. The caul assembly 82 includes an inner caul 84and an outer caul 86. The inner caul 84 has a contour generallycomplementary to rotor blade 20 at a position aligned with the leadingedge fairing 36 and the adjacent surface of the rotor blade 20. Theinner caul 84 is configured to conform the leading edge fairing 36 to adesirable structure. The outer caul 86 has a contour generallycomplementary to the inner caul 84 and is arranged concentrically withthe inner caul 84. When the first fixture 50 is installed about therotor blade 20, the outer caul 86 is arranged in contact with the firstand second bladder assemblies 70, 72.

Disposed between the outer caul 86 and the inner caul 84 is a heaterblanket 88. As a result of this location, the heater blanket 88 ismaintained in a more rigid state. Depending on the construction of theheater blanket 88, the heat generated by the heater blanket 88 may beconstant, or may vary across at least one of the span and the chord ofthe rotor blade 20.

A second fixture 90, may include a trailing edge guard 92 positionedabout the trailing edge 34 of the rotor blade 20, generally opposite thebond assembly 40. The trailing edge guard 92 includes an opening (notshown) generally complementary to the trailing edge 34 of the rotorblade 20 at a position substantially aligned with the splice capassembly 36. An interior of the trailing edge guard 92 may include aresilient liner (not shown), such as rubber for example, such that anypressure applied to the rotor blade 20 via the trailing edge guard 92does not damage the rotor blade 20. The second fixture may additionallyinclude a cuff guard 94 removably mounted to the blade cuff 38.

Extending from the first fixture 50 is at least one strap 96 configuredto restrict movement of the first fixture 50 relative to the rotor blade20. The length of the at least one strap 96 may be adjustable, such asvia a knob 98 for example, to tighten and loosen the strap 96 for easeof installation and removal of the bond fixture 50 about the rotor blade20. In an embodiment, the at least one strap 96 includes a loopconnectable at both ends to the frame 52 such that the loop isconfigured to encircle the rotor blade 20. In embodiments where atrailing edge guard 92 is used in conjunction with the bond fixture 50,the loop may extend about an exterior of the trailing edge guard 92, andin some instances may be received within a passageway 100.Alternatively, or in addition, a loop may extend about an exterior ofthe cuff guard 94, position within a passageway 102 formed therein torestrict sliding movement of the straps 96.

A method 100 of bonding the leading edge fairing 36 to the rotor blade20 is illustrated in FIG. 9. As shown in block 102, the leading edgefairing 36 is installed about the exterior surface of the rotor blade20. In an embodiment, installation of the leading edge fairing 36 mayinclude positioning a layer of release film over the leading edgefairing 36 and taping the release film in place. The release film may besubstantially larger than the size of the leading edge fairing 36 toprovide an adequate area to tape to the rotor blade 20. The caulassembly 80 is then installed over the release film, as shown in block104. In block 106, a trailing edge guard 90 is mounted about thetrailing edge 34 of the rotor blade 20, generally across from the caulassembly 80.

The bond fixture 50 is then mounted about the leading edge 32 of theassembly, as shown in block 108, in an overlapping configuration withthe caul assembly 80. In an embodiment, installation of the bond fixture50 additionally includes securing and/or tightening one or more straps92 of the bond fixture 50 about the rotor blade 20 to restrict movementof the bond fixture 50 and/or the trailing edge guard 90. In block 110,a power cable assembly and an airline connection are connected to auniversal controller. After testing of at least one of the power and apressure regulator, the universal controller operates the heater and thebladders to simultaneously apply pressure and heat to the leading edgefairing, as shown in block 112. After one or more bonding cycles arecomplete, the air is removed from the bladders and the bond fixture isremoved from the rotor blade, such as in a reverse order as previouslydescribed.

The bond fixture 50 illustrated and described herein provides localizedheat and pressure to a desired area of the rotor blade. The small sizeof the tool allows the bonding process to be performed in a fixedlocation without requiring movement to a separate location to cure. As aresult, the need for a large walk-in oven to cure components of theblade 20 is eliminated.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

What is claimed is:
 1. A bond fixture comprising: a frame defining achamber for receiving a component; at least one bladder assemblyconnected to the frame, the at least one bladder assembly including apad for contacting the component, wherein a position of the pad relativeto the component is controlled by a pressure of the bladder assembly;and a caul assembly adapted to thermally couple to the component to heata localized portion of the component.
 2. The bond fixture according toclaim 1, wherein the pad of the at least one bladder assembly has acontour complementary to the component.
 3. The bond fixture according toclaim 1, wherein the at least one bladder assembly includes a firstbladder assembly mounted to a first portion of the frame and a secondbladder assembly mounted to a second portion of the frame.
 4. The bondfixture according to claim 3, wherein the first bladder assembly and thesecond bladder assembly are arranged in fluid communication with apressure source.
 5. The bond fixture according to claim 3, wherein apressure is equalized between the first bladder assembly and the secondbladder assembly.
 6. The bond fixture according to claim 1, wherein thecaul assembly includes a heater.
 7. The bond fixture according to claim6, wherein the caul assembly further includes an inner caul and an outercaul and the heater is positioned between the inner caul and the outercaul.
 8. The bond fixture according to claim 6, wherein heat output bythe heater is uniform across the rotor blade.
 9. The bond fixtureaccording to claim 6, wherein heat output by the heater varies acrossthe rotor blade.
 10. The bond fixture according to claim 1, furthercomprising at least one strap associated with the frame to secure thebond fixture to the component.
 11. The bond fixture according to claim1, further comprising a trailing edge guard mounted to the componentopposite the frame.
 12. The bond fixture according to claim 11, whereinthe bond fixture and the trailing edge guard cooperate to affix to thecomponent.
 13. The bond fixture according to claim 11, furthercomprising a cuff guard mounted to a portion of the component, oppositethe frame.
 14. A method of bonding a leading edge fairing to a rotorblade comprising: installing the leading edge fairing about the rotorblade; mounting a bond fixture about the leading edge fairing; andapplying localized and constant heat and pressure to the leading edgefairing via the bond fixture.
 15. The method according to claim 14,further comprising installing a caul assembly about the leading edgefairing, the caul assembly being positioned within the bond fixture. 16.The method according to claim 14, wherein mounting the bond fixture tothe rotor blade includes tightening at least one strap about the bondfixture and the rotor blade.
 17. The method according to claim 14,wherein mounting the bond fixture to the rotor blade includes couplingthe bond fixture to at least one of a trailing edge guard and a cuffguard mounted to the rotor blade, opposite the bond fixture.
 18. Themethod according to claim 14, further comprising connecting a powersource to the bond fixture to apply heat to the leading edge fairing.19. The method according to claim 14, further comprising connecting anair supply to the bond fixture to apply pressure to the leading edgefairing.
 20. The method according to claim 19, wherein pressure appliedto the rotor blade by a pad is adjusted when air from an air supply isprovided to a bladder operably coupled to the pad.